Given a curve $\gamma(s)$ in $\mathbb{R}^{3}$, parameterised such that $\left\|\gamma^{\prime}(s)\right\|=1$ and with $\gamma^{\prime \prime}(s) \neq 0$, define the tangent $\mathbf{t}(s)$, the principal normal $\mathbf{p}(s)$, the curvature $\kappa(s)$ and the binormal $\mathbf{b}(s)$.

The torsion $\tau(s)$ is defined by

$$\tau=-\mathbf{b}^{\prime} \cdot \mathbf{p}$$

Sketch a circular helix showing $\mathbf{t}, \mathbf{p}, \mathbf{b}$ and $\mathbf{b}^{\prime}$ at a chosen point. What is the sign of the torsion for your helix? Sketch a second helix with torsion of the opposite sign.